Organic electroluminescence devices (organic EL devices) that make use of organic electroluminescence (organic EL) are composed of planar light-emitting layers comprising organic compounds that are formed on a transparent substrate, and they are increasingly being applied for use in thin displays. Compared to liquid crystal displays, organic EL displays that use organic EL devices have a wider viewing angle, consume less power, and have enough flexibility to be able to be softly bent, and therefore have considerable value for commercial use. Additionally, processes that use thin wafers (e.g., 1 μm) are also being developed in the field of 3D integration of ICs and in the field of MEMS.
However, thin substrates generally have a thickness of from 0.5 μm to 0.2 mm, and there are problems in the methods for transporting thin substrates during device fabrication. The substrate sizes may be chip-sized for smaller sizes, but are usually at least 4 inches square, and in large cases, they may be 1 m square or more. It is difficult to transport such thin substrates using robots or the like.
Therefore, one method that has been conceived is a method of transporting thin substrates by bonding them to the surfaces of transport substrates, in the form of glass substrates, films or wafers that are from about 0.1 mm thick to about 1.1 mm thick. This method has the advantage of allowing existing equipment to be used without modification. However, in the case of transport substrates, a device must be peeled from the transport substrate after completion.
There are three types of thin substrates. One type is thin glass, another is heat-resistant films as represented by polyimides. The third type is wafers. In some cases, wafers are protected by a tape to which a pressure-sensitive adhesive has been applied. In that case, the substrate is a laminate of a wafer and a film.
The currently proposed transport methods are methods using glass or wafers as carriers for transport. In the case of thin glass, because of the properties of glass with respect to glass, the bonding method involves direct bonding while keeping the carrier glass surface in a clean state.
In the case of a heat-resistant film, a film in which a destruction effect occurs when subjected to laser irradiation is formed between the transport glass and the film, and after bonding, the film can be separated by laser irradiation. Additionally, when the thin substrate is a wafer, non-contact transport methods and methods using special chucks have been proposed, but there are limits to the thickness that can be transported. The range of thicknesses that can be transported is around 100 μm, and there are no transport methods for thicknesses of 1 μm or so.
In this case, a method of using a transport substrate could be contemplated. However, there are no good separation methods. Additionally, in the case of a wafer, polishing may be used for thinning. In that case, an adhesive tape is adhered to the wafer in order to prevent cracking or chipping after polishing. In this case also, the use of glass as a carrier has been proposed.